Decadron in the treatment of cerebral abscess. An experimental study

European society of Clinical Microbiology and Infectious Diseases guidelines on diagnosis and treatment of brain abscess in children and adults

SCOPE

These European Society of Clinical Microbiology and Infectious Diseases guidelines are intended for clinicians involved in diagnosis and treatment of brain abscess in children and adults.

METHODS

Key questions were developed, and a systematic review was carried out of all studies published since 1 January 1996, using the search terms 'brain abscess' OR 'cerebral abscess' as Mesh terms or text in electronic databases of PubMed, Embase, and the Cochrane registry. The search was updated on 29 September 2022. Exclusion criteria were a sample size <10 patients or publication in non-English language. Extracted data was summarized as narrative reviews and tables. Meta-analysis was carried out using a random effects model and heterogeneity was examined by I2 tests as well as funnel and Galbraith plots. Risk of bias was assessed using Risk Of Bias in Non-randomised Studies - of Interventions (ROBINS-I) (observational studies) and Quality Assessment of Diagnostic Accuracy Studies 2 (QUADAS-2) (diagnostic studies). The Grading of Recommendations Assessment, Development and Evaluation approach was applied to classify strength of recommendations (strong or conditional) and quality of evidence (high, moderate, low, or very low).

QUESTIONS ADDRESSED BY THE GUIDELINES AND RECOMMENDATIONS

Magnetic resonance imaging is recommended for diagnosis of brain abscess (strong and high). Antimicrobials may be withheld until aspiration or excision of brain abscess in patients without severe disease if neurosurgery can be carried out within reasonable time, preferably within 24 hours (conditional and low). Molecular-based diagnostics are recommended, if available, in patients with negative cultures (conditional and moderate). Aspiration or excision of brain abscess is recommended whenever feasible, except for cases with toxoplasmosis (strong and low). Recommended empirical antimicrobial treatment for community-acquired brain abscess in immuno-competent individuals is a 3rd-generation cephalosporin and metronidazole (strong and moderate) with the addition of trimethoprim-sulfamethoxazole and voriconazole in patients with severe immuno-compromise (conditional and low). Recommended empirical treatment of post-neurosurgical brain abscess is a carbapenem combined with vancomycin or linezolid (conditional and low). The recommended duration of antimicrobial treatment is 6-8 weeks (conditional and low). No recommendation is offered for early transition to oral antimicrobials because of a lack of data, and oral consolidation treatment after ≥6 weeks of intravenous antimicrobials is not routinely recommended (conditional and very low). Adjunctive glucocorticoid treatment is recommended for treatment of severe symptoms because of perifocal oedema or impending herniation (strong and low). Primary prophylaxis with antiepileptics is not recommended (conditional and very low). Research needs are addressed.

Experimental animal models for brain abscess: a systematic review

BACKGROUND

Brain abscess (BA) is a rare, but severe infection and experimental BA animal models may prove crucial for advances in treatment. This review describes the development of experimental BA models and the clinical advances obtained from these, in a historical perspective.

MATERIAL AND METHODS

Experimental BA studies from inception until June 15, 2022, were included by searching the PubMed and Embase databases. Inclusion required the use of an experimental BA animal model. Non-bacterial BA models, in vitro studies, veterinarian case-reports, and articles written in non-English language were excluded. Bias was not systematically assessed, and the review was not registered at the PROSPERO.

RESULTS

79 studies were included. The majority of animal BA models have been based on small rodents using Staphylococcus aureus. The models have delineated the natural development of BA and provided detailed descriptions of the histopathological characteristics consisting of a necrotic centre surrounded by layers of inflammatory cells and fibroblasts encapsulated by a dense collagenous layer. Radiological studies of animal BA have been shown to correlate with the corresponding stages of human BA in both computed tomography and magnetic resonance imaging and may guide diagnosis as well as the timing of neurosurgical intervention. Moreover, pharmacokinetic studies of the intracavitary penetration of various antimicrobials have helped inform medical treatment of BA. Other studies have examined the diverse effects of corticosteroids including decreased cerebral oedema, intracranial pressure, and intracavitary drug concentration, whereas concerns on decreased or weakened capsule formation could not be confirmed. Finally, studies on the immunological response to BA have highlighted potential future immunomodulatory targets.

CONCLUSIONS

Animal models have been vital for improvements in the management of BA. Experimental BA models resembling human disease including polymicrobial infection by oral cavity flora in large animals are needed.

Brain abscess in children, a two-centre audit: outcomes and controversies

OBJECTIVE

The aim of this study was to better characterise clinical presentation, management and outcome in infants and children with brain abscess.

METHODS

The authors conducted a retrospective, multicentre study in two national reference centres over a 25-year period (1992-2017). During this period, 116 children and 28 infants (age <1 year) with brain abscess were treated.

RESULTS

The median age at diagnosis was 101.5 (range: 13-213) months in children and 1 (0-11) month in infants. Significant differences were observed between children and infants. The most common predisposing factor was meningitis in infants (64% of cases vs 3% in children), while it was otolaryngology-related infection in children (31% of cases vs 3.6% in infants). Infants presented more frequently with fever and meningism compared with children. 115 patients were treated with aspiration and 11 with excision. Reoperation was required in 29 children vs 1 infant. The overall mortality rate was 4% (3.4% for children, 7.1% for infants). At 3-month follow-up, the outcome was favourable in 86% of children vs in 68% of infants.

CONCLUSION

There is a clear difference between children and infants with brain abscess in terms of predisposing factors, causative organisms and outcome. Despite surgical drainage and directed antibiotic therapy, 25% of patients with brain abscess require reoperation. Mortality is improved compared with historical series; however, long-term morbidity is significant particularly in the infant population.

CT-guided drainage of a brainstem abscess in a cat as an emergency treatment procedure

Case summary

A 3-year-old male neutered domestic shorthair cat was presented with a 1-week progressive and rapidly deteriorating history of lethargy and abnormal behaviour. Neurolocalisation indicated multifocal intracranial lesions (right oculomotor nerve, brainstem [obtundation, non-ambulatory tetraparesis, vestibular dysfunction and intermittent decerebrate rigidity] and possibly the thalamus [left-sided pleurothotonus]), or more likely a single brainstem lesion with mass effect. MRI of the brain demonstrated a brainstem abscess causing severe dorsal displacement particularly affecting the pons and the medulla oblongata causing cerebellar vermis herniation through the foramen magnum. CT-guided free-hand technique drainage of the brain abscess was performed and broad spectrum antibiotics were started based on sensitivity results. The cat recovered uneventfully from anaesthesia displaying marked improvement immediately after the procedure. Antibiotics were continued for 8 months; repeat imaging prior to withdrawal found complete resolution of the brainstem abscess.

Relevance and novel information

Free-hand CT-guided drainage of a brainstem abscess is not without risk; however, in this case it led to significant clinical improvement and stabilisation likely owing to reduced intracranial pressure. It also provided a diagnostic sample that allowed successful medical treatment planning and outcome. To our knowledge, this is the first report describing the successful management of a brainstem abscess by CT-guided drainage in the veterinary literature. It suggests that stereotactic drainage followed by medical therapy can be considered a successful therapeutic alternative to brain surgery or medical treatment alone, providing an emergency treatment in cases of acute brainstem dysfunction.

Emergency Neurological Life Support: Intracranial Hypertension and Herniation

Sustained intracranial hypertension and acute brain herniation are "brain codes," signifying catastrophic neurological events that require immediate recognition and treatment to prevent irreversible injury and death. As in cardiac arrest, a brain code mandates the organized implementation of a stepwise management algorithm. The goal of this Emergency Neurological Life Support protocol is to implement an evidence-based, standardized approach to the evaluation and management of patients with intracranial hypertension and/or herniation.

Expressive aphasia caused by Streptococcus intermedius brain abscess in an immunocompetent patient

Background

Brain abscess is an uncommon but life-threatening infection. It involves a focal, intracerebral infection that begins in a localized area of cerebritis and develops into a collection of pus, surrounded by a well-vascularized capsule. Brain abscess still poses a significant problem in developing countries but rarely in developed countries. Predisposing factors vary in different parts of the world. With the introduction of antibiotics and imaging studies, the mortality rate has decreased between 5% and 15%. If left untreated it may lead to serious neurologic sequelae. The temporal lobe abscess can be caused by conditions like sinusitis, otitis media, dental infections, and mastoiditis if left untreated or partially treated. Additionally, in neurosurgical procedures like craniotomy, the external ventricular drain can get infected, leading to abscess formation.

Case presentation

We present the case study of an elderly female patient who presented with expressive aphasia caused by brain abscess, secondary to Streptococcus intermedius infection. The 72-year-old female with a medical history of hypertension came to hospital for evaluation with word-finding difficulty, an expressive aphasia that began a few days prior to presentation. Computed tomography of the head showed a left temporal lobe mass-like lesion, with surrounding vasogenic edema. The patient was empirically started on courses of antibiotics. The next day, she was subjected to magnetic resonance imaging of the brain, which showed a left temporal lobe septated rim-enhancing mass lesion, with bright restricted diffusion and diffuse surrounding vasogenic edema consistent with abscess. The patient was also seen by the neurosurgery department and underwent stereotactic, left temporal craniotomy, with drainage, and resection of abscess. Tissue culture grew S. intermedius sensitive to ampicillin sulbactam. Subsequently her expressive aphasia improved.

Conclusion

Brain abscess has a high mortality, however a significant proportion of patients with appropriately treated abscess recover completely and can survive without significant neurologic damage. Advanced imaging modalities may yield more accurate methods of differentiation of mass lesions in the brain. Biopsy of brain lesion with early initiation of appropriate antibiotics will change the outcome.

Emergency Neurological Life Support: Intracranial Hypertension and Herniation

Sustained intracranial hypertension and acute brain herniation are "brain codes," signifying catastrophic neurological events that require immediate recognition and treatment to prevent irreversible injury and death. As in cardiac arrest, a brain code mandates the organized implementation of a stepwise management algorithm. The goal of this emergency neurological life support protocol is to implement an evidence-based, standardized approach to the evaluation and management of patients with intracranial hypertension and/or herniation.

Bacterial brain abscess

Significant advances in the diagnosis and management of bacterial brain abscess over the past several decades have improved the expected outcome of a disease once regarded as invariably fatal. Despite this, intraparenchymal abscess continues to present a serious and potentially life-threatening condition. Brain abscess may result from traumatic brain injury, prior neurosurgical procedure, contiguous spread from a local source, or hematogenous spread of a systemic infection. In a significant proportion of cases, an etiology cannot be identified. Clinical presentation is highly variable and routine laboratory testing lacks sensitivity. As such, a high degree of clinical suspicion is necessary for prompt diagnosis and intervention. Computed tomography and magnetic resonance imaging offer a timely and sensitive method of assessing for abscess. Appearance of abscess on routine imaging lacks specificity and will not spare biopsy in cases where the clinical context does not unequivocally indicate infectious etiology. Current work with advanced imaging modalities may yield more accurate methods of differentiation of mass lesions in the brain. Management of abscess demands a multimodal approach. Surgical intervention and medical therapy are necessary in most cases. Prognosis of brain abscess has improved significantly in the recent decades although close follow-up is required, given the potential for long-term sequelae and a risk of recurrence.

Brain abscess

Brain abscess is a serious and life-threatening disease among children despite advances in diagnosis and management. Changes in the epidemiology of predisposing conditions for brain abscess are associated with changes in the patient population and causative organisms. Though still a potentially fatal infection, there have been recent improvements in diagnosis, treatment, and outcome. Although mortality appears to be decreasing, a significant percentage of children continue to have residual neurological deficits, including epilepsy, permanent motor or sensory dysfunction, visual field defects, and personality change. Some children also require placement of a ventriculoperitoneal shunt. The most common origin of microbial infection in children remains direct or indirect cranial infection arising from the middle ear, paranasal sinuses, or teeth. No prospective clinical trials have compared the various surgical and medical treatment strategies available to guide the management of cerebral abscesses in children. Most surgical and medical treatment guidelines are based on populations consisting primarily of adult patients. The use of corticosteroids for treatment of brain abscess is controversial. Anticonvulsants are recommended in children who have developed seizures potentially to prevent further episodes. Duration of anticonvulsant therapy should be individualized and guided by electroencephalographic (EEG) study in the follow-up phase of disease.

Emergency neurological life support: intracranial hypertension and herniation

Sustained intracranial hypertension and acute brain herniation are "brain codes," signifying catastrophic neurological events that require immediate recognition and treatment to prevent irreversible injury and death. As in cardiac arrest, evidence supports the organized implementation of a stepwise management algorithm. Because there are multiple etiologies and many treatments that can potentially reverse cerebral herniation, intracranial hypertension and herniation was chosen as an Emergency Neurological Life Support (ENLS) protocol.

Supratentorial and infratentorial brain abscesses: surgical treatment, complications and outcomes--a 10-year single-center study

OBJECTIVE

To analyze the variables determining morbidity, mortality and outcome in subjects with brain abscesses treated at a single center over a 10-year period.

METHODS

A retrospective study was conducted on a series of 59 patients with brain abscesses surgically treated with stereotactically guided aspiration or open craniotomy excision. Such variables as age, gender, clinical presentation, number of days to diagnosis, location, number of lesions, predisposing factors, mechanism of infection, etiological agent, and therapy were analyzed independently. Complications were defined as any deviation from the normal postoperative course occurring within 30 days of surgery, and classified according to a four-point gradual severity scale. Postoperative outcome was appraised through the Glasgow Outcome Scale (GOS) 6 months after surgery, 0-4 points were considered poor outcome and 5 points good outcome.

RESULTS

Eighty abscesses were diagnosed and surgically managed in 59 patients. The mean age was 44.69 years (range: 0.16-77); 59.3% were female. The median number of days to diagnosis was 7. Most frequent clinical presentations included fever (52.5%), headache (42.4%), and focal neurologic deficits (39%). Mechanism of infection was mainly hematogenous spread (32.2%). Stereotactically guided aspiration was the treatment of choice for 74.6% of the patients, whereas 25.4% of the cases were managed through open craniotomy excision. Outcome was favorable in 81.35% (n = 48) of the subjects. General morbidity was 27.1%, and mortality stood at 10.16%. Out of a total 38.98% (n = 23) of complications, two-thirds were due to medical causes. The analysis of variables revealed that only age (p = 0.02), immunosuppression (OR 5.83; p = 0.012) and hematogenous spread (p < 0.01) were associated with poor outcomes.

CONCLUSIONS

Immunosuppression, hematogenous spread and advanced age were predictors of poor prognosis. Most of the complications following brain abscess management were not directly related to surgery or surgical technique.

Tc-99m Labeled HMPAO white Blood Cell Scintigraphy in Pediatric Patients

OBJECTIVE

(99m)Tc labeled hexamethylpropylene amine oxime (HMPAO) white blood cell (WBC) scintigraphy is a frequently used option for acute infection, particularly in pediatric patients. This scintigraphy is applied to detect sites of infection/inflammation in patients with fever of unknown origin, to find and follow up osteomyelitis, and to detect suspicion of acute appendicitis. The aim of this retrospective study was to evaluate the value of (99m)Tc-HMPAO labeled WBC scintigraphy in pediatric patients.

MATERIAL AND METHODS

The study was conducted between January 2006 and December 2008 and included 13 patients (5 boys, 8 girls; mean age 6.9±6.2 years). Those patients who had suspicion of bone infection (n=7), fever of unknown origin (n=3), and suspicion of acute appendicitis (n=3) were evaluated retrospectively. (99m)Tc-HMPAO labeled WBC scintigraphy imaging was performed to all patients. Diagnosis was done according to operation and pathological results or clinical follow-up.

RESULTS

(99m)Tc-HMPAO labeled WBC scintigraphy has been found to be true positive in 6 cases, true negative in 6 cases, and false negative in one patient who had fewer unknown origin. The false negative case has been found to have encephalitis with MRI.

CONCLUSION

Leukocyte scintigraphy has been described as a useful diagnostic tool in the diagnosis of suspicion of bone infection, fever of unknown origin and suspicion of acute appendicitis. (99m)Tc-HMPAO labeled WBC scintigraphy is a rapid and very accurate method for detecting those pathologies. Our results showed that WBC scintigraphy might be reliably used for diagnosis of suspected bone infection and acute appendicitis, fever of unknown origin, and acute appendicitis, in pediatric patient population.

CONFLICT OF INTEREST

None declared.

Management of brain abscesses in children

Brain abscesses occur infrequently but continue to be problematic for the pediatric neurosurgical community. The incidence of brain abscesses in children has not changed much, although individual reports may show an increase or decrease in the number of reported cases depending on the patient population studied. An increase could be attributed to earlier detection due to advancements in imaging modalities and/or to an increase in the number of children with immunodeficient states caused by AIDS, chemotherapy for malignant lesions, and immunosuppressive therapy for organ transplantation. A decrease in the incidence of brain abscesses could be attributed to practices such as antibiotic treatment for otitis media, sinusitis, and/or prophylactic antimicrobial treatment for congenital heart disease in children. The morbidity and mortality rates associated with brain abscesses have not changed dramatically in the antibiotic and imaging era, and their preferred management can vary among healthcare providers. These lesions have been successfully treated by neurosurgeons. The causes of brain abscesses are highly variable in children, which is also the case in adults, but the predisposing factors in the pediatric population differ in prevalence. Cyanotic congenital heart disease, hematogenous dissemination, contiguous infection, and penetrating traumatic injuries are the most common causes of brain abscesses in children. In this review, the authors discuss the causes and medical and surgical management of brain abscesses in children.

Pyogenic brain abscess

✓ Brain abscesses have been one of the most challenging lesions, both for surgeons and internists. From the beginning of the computed tomography (CT) era, the diagnosis and treatment of these entities have become easier and less invasive. The outcomes have become better with the improvement of diagnostic techniques, neurosurgery, and broad-spectrum antibiotics. Atypical bacterial abscesses are more often due to chemotherapy usage in oncology, long life expectancy in patients with human immunodeficiency virus (HIV) infection, and immunosuppression in conjunction with organ transplantation. Surgical treatment options showed no significant difference with respect to mortality levels, but lower morbidity rates were achieved with stereotactically guided aspiration. Decompression with stereotactically guided aspiration, antibiotic therapy based on results of pus culture, and repeated aspirations if indicated from results of periodic CT follow-up scans seem to be the most appropriate treatment modality for brain abscesses. Immunosuppression and comorbidities, initial neurological status, and intraventricular rupture were significant factors influencing the outcomes of patients. The pitfalls and evolution in the diagnosis and treatment of brain abscesses are discussed in this study.

Glucocorticoid therapy in neurologic critical care

BACKGROUND

The pivotal role of inflammation and edema across the spectrum of central nervous system injury has driven extensive investigation into the therapeutic potential of glucocorticoids.

OBJECTIVE

To review the experimental and clinical data relating to the efficacy and adverse effects of glucocorticoids in conditions encountered in critical neurologic and neurosurgical illness.

DATA SOURCE

Search of MEDLINE and Cochrane databases, manual review of article bibliographies.

DATA SYNTHESIS AND CONCLUSIONS

The efficacy of glucocorticoids is well established in ameliorating edema associated with brain tumors and in improving outcome in subsets of patients with bacterial meningitis. Despite frequently encouraging experimental results, clinical trials of glucocorticoids in ischemic stroke, intracerebral hemorrhage, aneurysmal subarachnoid hemorrhage, and traumatic brain injury have not shown a definite therapeutic effect. The evidence supporting glucocorticoid therapy for spinal cord injury is controversial; however methylprednisolone continues to be widely employed in this setting.

Brain abscess in children

Brain abscess is a relatively uncommon but life-threatening infection in children. It can originate from contiguous site infections (eg, chronic otitis media, mastoiditis, sinusitis, meningitis), from distant pathologic states (eg, cyanotic congenital heart disease, chronic lung infections), after head trauma or neurosurgical procedures, or from cryptogenic sources. Predominant etiologic microorganisms vary depending on these predisposing factors. Computed tomography and magnetic resonance imaging are essential tools that enable the physician to make an accurate diagnosis of intracranial purulent collections. Proper selection of antimicrobial agents with good penetration of the central nervous system and with adequate coverage of both anaerobic and aerobic bacteria is critical for the medical management of brain abscess. Delay in surgical drainage can be associated with high morbidity and case-fatality rates. In the early phase of cerebritis, however, infection can respond to antibiotic therapy alone. Advances in diagnostic and therapeutic modalities during the last decade have improved the prognosis of this serious disease.

Stereotactic management of bacterial brain abscesses

BACKGROUND

CT and MR guided stereotactic techniques have provided promising results in the management of brain abscesses. We reviewed our results of stereotactic management of brain abscesses in 20 consecutive patients with 28 abscesses from 1986 to 1993.

METHODS

13 abscesses were in the cerebral hemispheres, 12 in the cerebellum, 2 in the pons and 1 in the thalamus. The bacterial organism was isolated in 12 of the 20 cases. All patients, except one who had a tuberculous abscess, were on antibiotics for less than 7 weeks.

RESULTS

Although there were 3 patients in coma before surgery, the mortality rate was zero and 17 patients had an excellent recovery with 3 patients having a persistent mild neurologic disability. Stereotactic aspiration of the largest lesion in the patients with multiple brain abscesses combined with intravenous antibiotic therapy was sufficient for the resolution of all lesions. Two of our patients treated with antibiotics alone showed abscess progression with neurologic worsening.

CONCLUSION

Stereotactic aspiration is safe, accurate, and when combined with the appropriate antibiotics, should be considered the procedure of choice in the management of brain abscesses.

Improved management of multiple brain abscesses: a combined surgical and medical approach

Bacterial brain abscesses occur in approximately 1500 to 2500 patients each year in the United States. Multiple abscesses have been noted in 10 to 50% of these patients. The goal of this study was to better define the roles of surgery and medical management in patients harboring multiple brain abscesses and to develop an algorithmic approach to the treatment of these complex patients. Between 1976 and 1992, 16 patients with multiple brain abscesses were treated by a single physician (M.L.R.). The ages of the patients ranged from 1.5 to 73 years (median, 47 yr). In all patients, a diagnosis of multiple abscesses was made by computed tomography (15 patients) or magnetic resonance imaging (1 patient) brain scans. The number of abscesses per patient ranged from 2 to 30, and the abscesses were located in all regions of the brain. Thirteen received a combination of antibiotics and surgical drainage, and three received antibiotics only. Surgery was performed on abscesses larger than 2.5 cm or on those situated in critical areas of the brain or causing significant mass effect. Excision and open aspiration via craniotomy and stereotactic aspiration were analyzed on the basis of the location of the lesion and infecting organism. Any abscess that enlarged after 2 weeks of antibiotics or that failed to shrink after 3 to 4 weeks of antibiotics was again aspirated or excised. Forty-three surgical procedures were performed in 13 patients, and 8 (62%) of the patients operated on required more than one surgical procedure. No significant morbidity was observed in any of the surgical procedures. Antibiotics were administered intravenously for an average of 6 to 8 weeks and were adjusted according to organism type and sensitivity to antibiotics. One patient (6%) died, and the remaining 15 patients had resolution of all abscesses and good neurological recovery within 6 months. On the basis of these results, we propose a combined surgical and medical approach to the treatment of patients with multiple brain abscesses. We recommend the aggressive surgical drainage of all abscesses larger than 2.5 cm in diameter, combined with 6 to 8 weeks of intravenous antibiotics. Biweekly computed tomography or magnetic resonance imaging is necessary to closely monitor patients for evidence of abscess growth or failure to resolve despite antibiotics, prompting another operation. The application of this combined approach should yield cure rates of more than 90% in patients with multiple brain abscesses, a result similar to that expected when treating patients with solitary lesions.

Management of brain abscess in children: review of 130 cases over a period of 21 years

The data on 130 children with brain abscesses treated over 21 years (1970-1990) were analyzed retrospectively. The whole group included four infants. Chronic ear infection and cyanotic congenital heart disease were the most common predisposing factors. In infants, meningitis and/or ventriculitis were dominant in the etiopathogenesis. Cases were evaluated according to the treatment received and also according to time periods. More than half of the patients (n = 74) in this series were treated by primary or secondary excision. Computed tomography (CT) facilitated the diagnosis and helped the planning of treatment. Aspiration gained increasing credit after the advent of CT. Microorganisms could be identified in 54% of the cultured specimens. Staphylococci, streptococci and Proteus were the dominating microorganisms. Penicillin and chloramphenicol have long been the mainstay of antimicrobial therapy but have recently been replaced by third-generation cephalosporins and sulbactam-ampicillin combinations. Overall mortality was 15.5% but showed a decline from 30% in the pre-CT era to 6% in the last 5 years and to zero in the last three. Neither the location nor associated heart disease contributed to the mortality, but mortality among infants was as high as 50%.

Further refinement of the Escherichia coli brain abscess model in rat

The rat brain abscess model provides a substrate for the modeling of delivery of therapeutic agents to intracerebral mass lesions. We now report refinement of the Escherichia coli brain abscess model in rat. A K1 surface antigen-negative E. coli isolated from human blood culture was stereotaxically inoculated into deep brain sites. Histopathologic analyses and quantitative cultures demonstrated the consistent production of lesions. No animal in this consecutive series developed meningitis, ventriculitis or sepsis. By contrast, prior experience with E. coli abscess production resulted in 25% failure rate of abscess production or death from sepsis. This improvement in the model may be attributable to specific characteristics of the bacteria used, modification of the inoculation method or the intracerebral placement technique. The present work suggests a reliable and consistent brain abscess model, which may be further used to study brain suppuration.

Clinical analysis and results of operative treatment of 41 brain abscesses

In this study, 41 cases of cerebral abscess operated on in our clinics between 1977 and 1986 were investigated retrospectively. The surgical strategy and the factors affecting the mortality rate were discussed. It was confirmed that the most important factor affecting the mortality rate was the consciousness level of patients in the preoperative period. The importance of computed tomography (CT) for early diagnosis and management of brain abscess is stressed.

The effect of steroids on gentamicin delivery to brain after blood-brain barrier disruption

Osmotic modification of the blood-brain barrier (BBB) provides an experimental model of vasogenic edema, is totally reversible, and does not cause any structural damage. In the present communication, the effect of corticosteroids on drug delivery to normal rat brain was evaluated in this model. Intraperitoneal dexamethasone was administered at doses ranging from 12 to 48 mg/sq m for 3 days; gentamicin delivery to the brain was then evaluated after either intravenous or intracarotid administration in both control and BBB-modified animals. Only animals receiving the highest dose of dexamethasone and in which the gentamicin was given intravenously demonstrated a statistically significant decrease in drug delivery. The effect of dexamethasone over a wide range of dosages, therefore, exhibited only modest effects on drug delivery to normal brain after osmotic BBB disruption.

Effect of dexamethasone on various stages of experimental brain abscess

Rats were inoculated with staphylococcus aureus to produce cerebral abscesses and treated with either antibiotic or dexamethasone and with antibiotic plus dexamethasone at sequential stages of abscess formation. Antibiotic alone shortened the cerebritis stage, accelerated the encapsulation and affected the bacterial clearance in the abscess centre when it was started early in the course of cerebritis. Dexamethasone impaired the lymphocytic and fibroblastic responses and delayed the collagen deposition as well as suppressed the efficacy of antibiotic. However, it did not halt entirely the encapsulation and did reduce the associated cerebral oedema.

Treatment of experimental brain abscess. 2. Effects of combinations of hyaluronidase with antibiotics and dexamethasone

Brain abscess formation was studied experimentally in rats to determine the most appropriate nonsurgical treatment method by applying different combinations of hyaluronidase, dexamethasone and antibiotic sensitive to the inoculated bacteria in various stages of classical abscess development. The results showed that combined therapy with antibiotic and hyaluronidase started the day before inoculation averted the formation of brain abscess and the same therapy started after encapsulation, effectively eliminated the organisms and resolved the infection leaving a glial scar. But the same therapy, only started at the cerebritis stages, caused an increase of cerebritis. The addition of dexamethasone reduced the oedema but enhanced the cerebritis and delayed encapsulation. Though neurosurgical intervention continues to be the definitive method for eradicating the infection and preventing the pressure-related complications of brain abscess, our concept of management with hyaluronidase and appropriate antibiotic might be a new effective chemotherapeutic method of encapsulated brain abscesses in selected high-risk patients.

Cerebral toxoplasmosis in the acquired immune deficiency syndrome

We examined the clinical and pathological features of 26 patients who presented with a diagnosis of CNS toxoplasmosis. Patient data was analyzed with respect to demographics, clinical presentation, treatment course and pathology. Patients presented with a wide variety of signs and symptoms. All patients had positive serum antitoxoplasma IgG; ring enhancing lesion(s) were present on all but one brain CT scans. A series of guidelines in the management of CNS toxoplasmosis in AIDS patients are presented. Prior to biopsy, patients with positive serology and characteristic CT scans should receive two weeks of treatment. Biopsy is indicated in those cases with negative serology, atypical presentation, progressive clinical deterioration, or differential response of lesions to empiric therapy.

Treatment of intracranial abscesses associated with sinusitis in children and adolescents

We retrospectively reviewed the management of intracranial abscesses associated with sinusitis in 13 children and adolescents by reviewing medical records and computed tomography (CT) scans of a consecutive case series. The mean duration of follow-up was 4.5 years with a range of 1.3 to 8.6 years, and the setting was a major metropolitan children's hospital providing primary as well as tertiary care. All patients received antibiotics (most commonly chloramphenicol, 75 to 100 mg/kg/day, in combination with oxacillin, 150 to 200 mg/kg/day) to which the sinus and intracranial organisms are susceptible. Surgical drainage of loculated infection was done for patients with acute neurologic symptoms or signs and for those patients whose abscesses enlarged during medical therapy. Three patients underwent immediate drainage of intracranial abscesses because of acute neurologic signs and symptoms. Sequential CT scans demonstrated enlargement of the intracranial abscesses in the remaining 10 patients. This apparent failure of medical management could not be explained by duration of symptoms before therapy, size of lesion, choice of antibiotics, or use of steroids. No child was successfully treated with antibiotics alone. Successful management consisted of antibiotic therapy combined with surgical drainage of loculated infection. This approach to therapy is preferred for all children with intracranial abscess associated with sinusitis.

Treatment by aspiration of brain abscesses

Sixteen patients, with a total of 18 abscesses, were treated by aspiration and systemic antibiotic therapy, to which antiepileptic prophylaxis and corticosteroids were added. Diagnosis of the abscesses and monitoring of their evolution relied principally upon computed tomography; this technique was also used per-operatively when aspirating small abscesses. Bacteriological examinations were positive in all our cases and a polymicrobial flora was found in half of these. One or, eventually, two aspirations within the same week were sufficient, in most cases, to promote healing. Nevertheless, in three patients, the abscesses, however sterilized, did not show any volume reduction, probably because of adhesions to the dura mater, of a large part of the abscess surface area. One patient died from concomitant cardiac disease and one patient remained seriously disabled. Epilepsy was observed as a sequela, in six patients. This study emphasizes the role of neuroradiological and bacteriological examinations, whilst surgery may be restricted, in most cases, to a simple aspiration.

Effect of dexamethasone on experimental brain abscess

Dexamethasone has been used to manage brain edema in patients with intracranial abscess. However, its administration has often been delayed or avoided for fear of adverse effects upon normal host responses to infection. An experimental model of brain abscess in the rat was developed to determine if dexamethasone produced adverse effects on immune competence and collagen deposition in the region of the abscess. Sprague-Dawley rats were inoculated with Staphylococcus aureus and treated intraperitoneally each day with either dexamethasone (0.25 mg/kg) or saline solution. Surviving animals were sacrificed at 4, 8, 12, or 18 days after treatment. The brains were examined grossly for abscess formation and microscopically for intensity of the inflammatory response, abscess diameter, and wall thickness. There were no differences in mortality rates, abscess production rates, or abscess diameters when groups were compared. The intensity of inflammatory response was similar in both groups. In the group sacrificed 8 days after inoculation, a delay in collagen deposition was apparent, manifested as a thinner abscess wall in the experimental group (mean: 17.8 mu in dexamethasone-treated animals and 85 mu in saline-treated control animals: p = 1.0041). At 12 and 18 days after inoculation, there was no difference in abscess wall thickness between the control and experimental groups. Therapeutic doses of dexamethasone had little effect on mortality rates, incidence of abscess production, or intensity of inflammatory response in the experimental animals. Thus, dexamethasone did cause a delay in collagen deposition in the walls of experimental brain abscesses, but wall thickness 18 days after inoculation was not affected.

Experimental brain abscess development in the chronically immunosuppressed host. Computerized tomographic and neuropathological correlations

The neuropathological progression of brain abscess formation was studied experimentally in paired immunosuppressed and control dogs. The immunosuppressed animals received azathioprine and prednisone beginning 7 days prior to intracerebral inoculation with alpha streptococcus. Histological findings were correlated with computerized tomography (CT) brain scans. The evolution of brain abscess in the immunosuppressed animals could be divided into three stages based on histological evaluation: cerebritis stage (1 to 11 days), early-capsule stage (12 to 17 days), and late-capsule stage (18 days and later). There was a significant delay in the evolution of alpha streptococcus brain abscess compared to the authors' previous studies. Histologically, abscesses in immunosuppressed dogs were characterized by a decrease and delay in collagen formation, a reduction in polymorphonuclear leukocytes and macrophages, longer persistence of bacterial organisms, and an increase in gliosis. During the cerebritis stage, abscesses in control animals were consistently larger and more edematous than those in immunosuppressed animals and reached their maximum size by Day 8, whereas abscesses in immunocompromised animals reached their maximum size around Day 12. In the late-capsule stage, abscesses in immunosuppressed animals remained larger than those of control animals and continued to show signs of delayed development. This was evidenced by diffusion of contrast medium into the lucent center of ring-enhancing lesions on delayed CT scans. The results suggest that the decreased inflammatory response and edema formation in the immunosuppressed host resulted in less initial mass effect from brain abscess, but that the eventual size and area of the abscess may have become larger due to the less effective host response.

Conservative and surgical management of focal cerebral infection

After the introduction of CT-scanning the management of focal cerebral infections has been modified. Based on the data of two patients and on the literature the authors discuss the choice between fully conservative, immediately neurosurgical or delayed neurosurgical treatment. It is the author's opinion that by closely following the infectious process too early neurosurgical intervention can be avoided and thus unnecessary sacrifice of viable neural tissue.

Experimental anaerobic brain abscess. Computerized tomographic and neuropathological correlations

The neuropathological progression of brain abscess formation induced by a mixed anaerobic culture of Bacteroides fragilis and Staphylococcus epidermidis was studied experimentally in dogs. Histological findings were correlated with computerized tomographic (CT) brain scans. The evolution of brain abscess formation could be divided into three stages based on histological criteria: early cerebritis (Days 1 to 3); late cerebritis (Days 4 to 9); and capsule formation (Day 10 and later). Capsule formation could not be divided into early and late stages because encapsulation was delayed compared with a previously reported model of alpha-Streptococcus brain abscess. Histologically, there was evidence for a very virulent infection. Leptomeningitis was significant even in the late stages. Early ventricular rupture occurred in 25% of the animals. A pattern of extensive purulent encephalitis was seen in 25% of the animals. In the early cerebritis stage, blood vessels near the necrotic center were engorged and were surrounded by hemorrhage and/or protein-rich fluid. Cerebral edema was extensive. Although fibroblasts appeared in late cerebritis, there was marked delay of capsule formation. Three-week-old lesions still had areas of incomplete capsule formation and foci of uncontrolled infection. In the cerebritis stages, CT scans showed an area of ring enhancement which was incomplete on early scans (at 5 minutes after injection of contrast material) but partially filled in and thickened on delayed scans (at 20 to 45 minutes). On even later delayed scans there was no decrease in intensity of ring enhancement. Lesions in which capsule formation occurred also showed ring enhancement, but delayed scans showed a decrease in the intensity of enhancement. The lesions that ruptured into the ventricular system showed atypical CT findings, with either lack of contrast enhancement (histologically there was minimal cerebritis adjacent to the abscess cavity) or a marked delay in contrast enhancement (cerebritis was more extensive and corresponded to the width of ring of enhancement). This study suggests that Bacteroides fragilis is a virulent organism in the brain. The developing abscesses enlarged quickly, were prone to early ventricular rupture, and showed incomplete and delayed encapsulation.

Current concepts of bacterial infections of the central nervous system. Bacterial meningitis and bacterial brain abscess

Investigative work continues to provide guidance toward more rational management of bacterial meningitis and bacterial brain abscess. An increased understanding of the host's response in cases of bacterial meningitis has established that diffusibility of an antibiotic into the cerebrospinal fluid (CSF) is necessary, but is not sufficient for microbial cure. The antibiotic must also have a bactericidal effect on the pathogen. Meningitis after neurosurgery may be caused by Gram-negative aerobic bacilli. In some of these cases the newer cephalosporin antibiotics may be a useful advance. Meningitis complicating ventricular CSF shunts presents a paradigm for the problem of eradicating foreign body-related infections. Studies of the interaction of the host, the organism, and the shunt material offer some explanation for the limited efficacy of antibiotics observed in this setting. There have been advances in microbial definition of bacterial brain abscess. The identification of Bacteroides fragilis as a pathogen in certain brain abscesses has established a role for a newly available antibiotic, metronidazole. The study of the pathological distinction between cerebritis and frank abscess is clarifying two clinical characteristics of brain abscess: the limited success of antibiotic treatment and the increase in intracranial pressure. Computerized tomography has offered a valuable clinical "look" at brain abscesses; however, there are still problems in correlating the scan images with the evolving pathological process.

Short term, high dose corticosteroids in computed tomographic staging of experimental brain abscess

A short term, high dose corticosteroid treatment protocol was investigated to determine its clinical utility in staging an experimental brain abscess. Corticosteroids were shown to decrease the degree of contrast enhancement of brain abscess 12 h after administration but the magnitude of the effect was not consistent enough to be clinically useful in staging. The corticosteroid effect progressively diminished as the inflammatory lesion encapsulated over time. This effect emphasized that a decreasing ring diameter and not diminished contrast enhancement should be the CT criterion for brain abscess resolution.

Neuropathological and computerized tomographic findings in experimental brain abscess

The neuropathological progression of brain abscess formation was studied experimentally at sequential stages in dogs, and the findings correlated with the appearance on computerized tomographic (CT) brain scans. The evolution of brain-abscess formation was divided into four stages based on histological criteria: early cerebritis (Days 1 to 3); late cerebritis (Days 4 to 9); early capsule (Days 10 to 13); and late capsule (Days 14 and later). The cerebritis stage was characterized by prominent perivascular cuffing by inflammatory cells in the area adjacent to the developing necrotic center. However, the early elements of capsule formation appeared with the presence of fibroblasts by Day 5. The CT scans showed ring-shaped contrast enhancement by Day 3. Delayed scans at 30 minutes revealed diffusion of the contrast material into the developing necrotic center, forming a solid lesion. In lesions that were well encapsulated (14 days and older), five distinct histological zones were apparent: 1) a well formed necrotic center; 2) a peripheral zone of inflammatory cells, macrophages, and fibroblasts; 3) the dense collagenous capsule; 4) a layer of neovascularity associated with continuing cerebritis; and 5) reactive astrocytes, gliosis, and cerebral edema external to the capsule. The CT appearance of well encapsulated abscesses showed a typical ring-shaped contrast-enhancing lesion. On the delayed scans, the "ring" did not fill in with contrast enhancement. The diameter of the ring correlated best with the presence of cerebritis (perivascular infiltrates in the adventitial sheaths of vessels surrounding the abscess). The discussion focuses on the relevance of this study to the current management of patients with brain abscess.

Evolution of brain abscess in cats formation of capsule and resolution of brain edema

Brain abscess evolution was studied in an experimental model in the cat correlating the computed tomographic scan appearance with intracranial pressure, brain edema and histopathological findings. Brain inflammation was produced by direct inoculation of Staphylococcus aureus into the white matter. Abscesses developed in all animals. The ring enhancement around the necrotic focus seen at an early stage after contrast-medium injection cannot be equated with capsule formation as long as the abscess diameter increased. Parallel to the acute stage of abscess, the intraventricular pressure increased due to the rising mass effect and the spreading edma. The morphological investigations revealed on the seventh day an extreme enlargement of extracellular spaces with immense amount of edema fluid, rich in protein and fibrin. Some blood vessels in the close vicinity of the abscess showed gaps within the endothelial cell layer. When encapsulation developed, ring enhancement became more homogeneous and decreased in diameter. In spite of encapsulation, a circumscribed disturbance of the blood-brain barrier persisted which was responsible for a belated resolution of edema and a slow decrease of intracranial pressure. Only therapy with dexamethasone could effect a marked change in the course of the disease.

Nonoperative treatment of brain abscesses in selected high-risk patients

✓ In a series of eight high-risk patients, presumed intraparenchymal pyogenic brain abscesses resolved or decreased markedly in size with antibiotic therapy and without surgery. Cases were selected for antibiotic trial because of multiplicity or location of the abscesses and complicating medical conditions. Patients were alert or lethargic, with stable or improving early clinical courses. Diagnosis was made by computerized tomography (CT) brain scans and corroborative laboratory and diagnostic studies. Cases were closely monitored with serial CT scans. In six cases, bacteria were cultured from blood, cerebrospinal fluid, or fluid aspirated from one of multiple abscesses. Antibiotics were selected for specificity against the cultured organism, or consisted of high-dose penicillin plus chloramphenicol; therapy continued for a median of 7 weeks.

Serial CT scans showed decreased abscess size by a mean of 2.4 weeks (range, 1 to 4 weeks) and resolution of contrast-enhancement and mass effects by a mean of 9.8 weeks (range, 8 to 14 weeks). Abscesses followed to resolution were significantly smaller (mean, 1.7 cm diameter, p < 0.01) than those not responding to similar courses of antibiotic therapy (mean, 4.2 cm diameter). Two patients died of causes unrelated to their abscesses; surviving patients have no neurological deficit (mean follow-up period, 25 months; range, 15 to 37 months). Guidelines are recommended for a treatment protocol to be cautiously applied for high-risk patients with small abscesses. Surgery is recommended in all other cases of pyogenic brain abscesses.

Relevance of antibiotics in the treatment of brain abscesses. Report of a case with eight simultaneous brain abscesses treated and cured medically

A case of eight simultaneous brain abscesses in the right cerebral hemisphere, treated medically after puncture of two of them, is reported. Antibiotics and hypertonic mannitol and, after seven days, dexamethasone were sufficient to cure these lesions. CT scan was of primary importance to follow the evolution under treatment. To get the best efficiency from antibiotics, identification of the microorganism and assessment of its resistance to antibiotics are necessary. It is suggested that in certain conditions medical therapy might be sufficient to treat cerebral abscess, after simple puncture to isolate the infecting agent. Corticosteroids should be avoided in the acute phase because they prevent antibiotics from penetrating the abscesses.

Cerebral abscesses produced by bacterial implantation and septic embolisation in primates

The degree of brain abscess encapsulation is positively related to surgical mortality and methods to enhance capsule wall formation, therefore, have therapeutic relevance. Two primate models are described which may be useful in the investigation of encapsulation of traumatic and metastatic brain abscesses. Direct intracerebral inoculation induces abscesses displaying more prominent inflammatory responses and encapsulation than does septic embolisation, despite similar abscess age and size. Cerebral ischaemia surrounding metastatic suppurative foci may retard capsule wall formation.

Role of vascular proliferation on angiographic appearance and encapsulation of experimental traumatic and metastatic brain abscesses

Experimental traumatic abscesses were produced in rhesus monkeys by intracerebral injection of nutrient agar contaminated with Staphylococcus epidermidis, and metastatic abscesses were induced by intracarotid embolization of silicone cylinders contaminated with Staphylococcus epidermidis. All monkeys underwent preoperative and serial postoperative carotid angiography. Traumatic abscesses produced early capsular blushes and progressive anterior cerebral artery displacements. Metastatic abscesses induced transient midline shifts but no capsular stains. Postmortem studies on the monkeys showed that mean capsular thickness and segmental wall vascularity of the traumatic and metastatic abscesses were significantly different (p less than 0.001), despite equal abscess ages and similar abscess volumes. In comparison to traumatic abscesses, metastatic abscesses demonstrated reduced inflammatory cell infiltration and retarded collagen formation around proliferating capsular vessels. Brain surrounding the metastatic abscesses demonstrated ischemic changes. The results suggest that 1) capsular blushes during cerebral angiography are secondary to vascular proliferation within the capsule and not to compression of surrounding brain, 2) vascular staining reflects capsular thickness, 3) capsular vascularity contributes to collagen formation, 4) encapsulation is dependent upon the integrity of surrounding brain, and 5) adjacent cerebral ischemia may impede inflammatory responses involved in capsule formation.